Hi Pete,
I've noticed the same thing. My 100W-and-wire signal gets picked up
by skimmers just before a contest, but after the starting gun I hardly
ever get spotted.
Has anyone done tests to measure the "capture" behavior of CW Skimmer?
By that I mean something like setting up three stations, and
measuring how well CWS "captures" a weaker signal wedged between two
stronger ones. How far apart do they have to be, as a function of
relative signal strength, for a signal to be recognized for subsequent
decoding -- that kind of stuff. One explanation might be that the
crowded conditions of contest bands simply cause the software to miss
the weaker signals as it "scans" the band for things to decode. The
Morse system I built back in the 70s had such behavior; it used PLLs
to lock on to signals, and nearby stronger signals would prevent it
ever locking on to a weaker signal, even though the weaker one was
quite audible. (We improved things by using very narrow filters and
time-reversal of the data stream to pull out marks and spaces)
73,
/Jack de K3FIV
On Tue, May 28, 2013 at 4:43 AM, Pete Smith N4ZR <n4zr@contesting.com> wrote:
> Hi Hank - to the best of my knowledge there is no such "desensing"
> phenomenon with CW Skimmer or Skimmer Server. During the contest, there were
> both a large number of six-band-at-once Skimmers (using QS1Rs, mostly) and a
> large number of one-band-at-a-time Skimmers using everything from Softrocks
> to QS1Rs to Perseus receivers. The single-banders consume relatively little
> computer power, as you can imagine, while the multi-banders use much more.
> In theory, if a Skimmer has too many decoders working at once, so that its
> CPU utilization hits 100 percent, it will not decode them all until the rush
> subsides. It is also possible that something as yet undiscovered may have
> caused not all spots to be passed on to the RBN's Telnet servers, but we
> have had no indication of this, and the sheer volume of spots that *were*
> forwarded suggests this is unlikely.
>
> There are a couple of other possible explanations for why you were not
> successful in triggering more spots. You *must* use either "CQ" or "TEST"
> in your CQs, with no more than one other word between the keyword and your
> call, or else Skimmer doesn't know if you are CQing. QRM could have reduced
> the number of spots, simply because stations that you couldn't hear at your
> QTH were QRMing you in places like Europe, where there is the greatest
> concentration of RBN Skimmers. Or possibly, the times when you were trying
> to run were ones where you did not have propagation to large numbers of
> Skimmers.
>
> I'm sorry, I know probably none of these answers is satisfactory. I'd love
> to hear other possible explanations, if anyone has them.
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
>
>
> On 5/27/2013 11:21 PM, Hank Greeb wrote:
>>
>> I had a terrible time trying to make a "run" when I tried now and then
>> during the recent CQ WPX contest. I'd call CQ for as long as 10 minutes,
>> and only once did I get more than one or two contacts in a row from trying
>> to "run." I figured that propagation was weird, but couldn't figure out
>> what the deal was.
>>
>> After the fact I searched for my call in the past 24 hours, and found that
>> I had rarely been heard calling CQ by any of the skimmers on the Reverse
>> Beacon Network, and even more rarely was I more than 10 dB above ambient
>> noise. I've had considerably better results in other recent contest
>> efforts. On a typical day, if no contest is in progress, I can call CQ two
>> or three times in a minute, and I'd be heard by numerous skimmers, with my
>> poorer home location.
>>
>> I figured that the skimmers must have been overloaded, or the fact that
>> thousands of folks were calling CQ was overloading their capacity to dig
>> down for the weaker stations.
>>
>> In comparing my results, hour over hour compared to last year, I made
>> "about" the same number of Q's per hour - >99.44% of the S&P, so it would
>> appear that, even with lousy ionospheric conditions, I was able to S&P with
>> similar effectiveness. Last year, at home, with just a low wire antenna, I
>> didn't even try "running" so I don't know if I was being heard by the
>> skimmers.
>>
>> Is it possible that the sheer number of signals on the air make the
>> skimmers less sensitive? Or is my thinking all wrong?
>>
>> 72/73 de n8xx Hg
>> QRP >99.44% of the time
>> Operated WQ8RP during CQ WPX 2013
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>
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